Extraction process

ABSTRACT

A SOLVENT EXTRACTION PROCESS, MORE PARTICULARLY A FURFURAL EXTRACTION PROCESS WHEREIN A PORTION OF THE EXTRACT PHASE IS WITHDRAWN FROM THE EXTRACTION ZONE, CONCENTRATED AND COOLED BY EVAPORATION OF PART OF THE SOLVENT CONTAINED THEREIN AND BY COOLING MENS AND RETURNED TO THE EXTRACTION VESSEL, THEREBY ENHANCING THE AROMATICPARAFFINIC SEPARATION TAKING PLACE THEREIN.   D R A W I N G

July |B STElNME-rz ETAL 3,825,489

EXTRACT ION PROCES S Filed No'v. 21, 1972 Patented July 23, 19743,825,489 EXTRACTION PROCESS Ib Steinmetz, Wilmington, Del., and WilliamWayne Wentzheimer, Glen Mills, Pa., assignors to Sun Oil Company ofPennsylvania, Philadelphia, Pa.

Filed Nov. 21, 1972, Ser. No. 308,377

Int. Cl. C10g 21/16 U.S. Cl. 208-327 2 Claims ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION 1. Field of the invention This inventionrelates to a process for effecting solvent extraction of hydrocarbonoils containing aromatic components to prepare an aromatic concentrate.More particularly this invention relates to said extraction usingfurfural.

2. Description of the prior art Extraction of aromatic components fromhydrocarbon oils with furfural or other solvents is well known. Theextraction is usually conducted at temperatures wherein both theraffinate and extract are in a fluid, easily handled liquid phase. Thearomatic hydrocarbons are dissolved by the solvent and separated fromthe mixtures as the rich extract phase from which the aromatics arefurther separated by distillation and, in a commercial process, thesolvent is recirculated to the extractor. The parainic and naphthenichydrocarbons from the raffinate phase which also contain smallquantities of the solvent are also generally processed by distillationin a commercial process with the solvent being recirculated to theextractor.

One problem which arises in furfural extraction of lube stocks toproduce lubricating oils and extract oil is reaching an acceptablearomatics content and a low wax content in the extract while producinghigh viscosity index lubes in the rainate stream.

SUMMARY OF THE INVENTION We have now discovered a process whereby thearomatic content in the extract product is substantially increased whichcomprises:

(a) solvent extracting of a hydrocarbon feed in an extraction zone,

(b) withdrawing a portion of the extract phase from said extractionzone,

(c) evaporating a portion of the solvent contained in said extract phasein a separation zone and removing said evaporated solvent from theprocess,

(d) recycling the remaining portion of said extract phase, now rich inextract product, through a cooling zone, and

(e) returning said cooled, concentrated extract phase to the extractionzone thereby enhancing the separation taking place therein.

DESCRIPTION OF THE DRAWING AND THE PREFERRED EMBODIMENT A more completeunderstanding of the invention may be had from a consideration of theaccompanying drawing which is a schematic flowsheet of the preferredembodiment of the invention.

A hydrocarbon oil feed containing aromatic and parafnic components to beseparated from each other, enters the solvent extractor 1, via line 2. Asuitable solvent, normally an organic liquid which preferentiallydissolves aromatic hydrocarbons from hydrocarbon mixtures containingsame in admixture with paraflinic or naphthenic hydrocarbons, enterssaid extractor via line 3. The preferred solvent is furfural but otherorganic compounds meeting the above criterion may also be employed, e.g.phenol.

A portion of the solvent and aromatic compounds which comprise theextract phase is withdrawn from the extractor via line 4 usuallycontaining 80-95% solvent and enters a series of separation zones 5 and6. In each zone, solvent is separated by an evaporation mechanism,withdrawn overhead via lines 7 and 8 and sent to a solvent storage ormake-up tank, not shown. The solvent thus separated is then handledsimilarly to other solvent streams in the solvent recovery system, andreused in the extraction. The bottom stream from said series ofseparation zones, which can also be one larger separation zone passesthrough heat exchanger 11 countercurrent to extract bottoms withdrawnfrom extractor 1 via line 10. The concentrated extract continues vialine 9 through cooling means 12 and is recycled to extractor 1. Theusual solvent content of the stream now in line 9 is 10 to 2O percent.The cooler more concentrated extract changes the equilibrium in theextractor zone resulting in a more concentrated extract phase beingwithdrawn via line and being sent through cooler 11 and to productsolvent separator 13. Here, the remaining solvent is removed, via line14 usually with steam, and the final extract product is withdrawn vialine 15.

The rafiinate phase withdrawn from extractor 1 via line 16 passesthrough a series of separation zones 17, 18 and 19 and is separated fromthe solvent usually with steam. Improving the purity of the extractproduct by the inventive process also results in improved purity of theraffinate which is withdrawn via line 20. The remaining solvent iswithdrawn via line 21. It should be noted that the series of separationzones 17, 18 and 19 shown can also be one larger separation zone.

Example 1 As shown in Table 1A, an extract product (Lagomedio) from aconventional extraction process run at 220 F. having 84 wt. percentaromatic contained therein was subjected to additional solvent treatmentat varied temperatures to show the increase in aromatic content whichcan be achieved by the process of the present disclosure. In thefollowing runs, the temperature is decreased as would result fromoutside cooling of an extract recycle.

As shown in Table 1B, a second extract product (Mid- Continent) from aconventional extraction process having 69 wt. percent) aromaticscontained therein was treated as in Example 1 except that the solventdosage was varied as well as the temperature.

TABLE 1B Solvent Aromatics Change in dosage, wt. percent aromatic,Temperavol. percent in extract wt. percent Run number ture, F. chargeproduct over charge Table 1A shows the step-wise increase in aromaticscontent of the extract as the temperature is lowered in increments of 10F. from Run 1 to Run 4 at yconstant solvent dosage. Table IB shows theeifect of decreasing temperature at two different solvent dosage levels.Runs 5 and 7 are at 90/vol. percent and Runs 6 and 8 are at 75 vol.percent. In both sets, an increase in aromatics wt. percent is seen asthe temperature is decreased.

Desired product specications can be met by variation of solvent dosageand chill temperature by one reasonably skilled in the art utilizing theinventive teaching disclosed herein.

We claim:

1. In a process comprising contacting, in an extraction zone, ahydrocarbon mixture, which contains aromatic and parafnic compounds,with a solvent which preferentially dissolves said aromatic compoundsand separating said hydrocarbon mixture into a rst aromatic extractprises: n

(a) withdrawing a second aromatic extract stream from said extractionzone, (b) evaporating part of the solvent from said second aromaticextract streamin an evaporation zone, (c) withdrawing solvent streamfrom said evaporation zone,v 1 (d) withdrawing a cooler moreconcentrated second aromatic extract stream from said evaporation zone,(e) cooling the concentrated aromatic extract stream in a cooling zoneand recycling said cooler more concentrated second aromatic extractstream to said extraction zone. 2. The process of Claim 1 wherein thesolvent used is furfural.

References Cited UNITED STATES PATENTS 2,161,567 6/1939 Gee et al.208-320 2,851,395 9/1958 Kiersted et al. 208-320 3,251,767 5/1966Stewart 208-320 3,546,093 12/ 1970 Wentzheimer et al. 208-327 DELBERT E.GANTZ, Primary Examiner C. E. SPRESSER, IR., Assistant Examiner Us. C1.XR.

20s-318, 319, 32o, 321; 26o-674 sa.

